1. Field of the Invention
The present invention generally relates to a vehicle transmission shifting mechanism for motorized vehicles. More particularly it relates to a rotary indexing shifting mechanism for a motorized vehicle transmission having means to place the transmission in a neutral, or any forward or reverse gears.
2. Description of the Prior Art
There have been many improvements over the years in manual shift multi-speed transmissions, including improvements relating to the shifting of sliding gear manual transmissions. Shift mechanisms generally include a shift stick or pivotal shift lever associated with a series of linkages to engage or disengage the gears of the transmission. In a typical prior art shifting mechanism, the shifting lever controls the movement of parallel shifting linkages through a mechanical means resulting in longitudinal sliding of the shift linkages. Typical 5-speed transmissions having reverse require two such linkages, and the required number of linkages increases as the number of gear ratios available from the transmission increases. Shifting is accomplished through lateral and longitudinal movement of the shift control lever, typically in an "H" pattern for a 5-speed transmission, to engage the transmission in a selected gear. The lateral and longitudinal movement of the shift control lever increases and the number of gear ratios available from the transmission increases. Typical multi-speed transmission utilize shifting forks to axially drive the gears into engagement where each shifting fork is capable of engaging two gears. The plurality of shifting forks required for transmissions having more than two speeds are fixed through attachment means to the parallel shift linkages. Longitudinal movement of the shift linkages results in engagement of the transmission in the desired gear. This shifting mechanism including the parallel shift linkages is limited in applications due to its bulk and weight.
One disadvantage of this arrangement is that the parallel shift linkages must be stiff and rigid to control the engagement and disengagement of the gears of the transmission. Typically this limits application of the shifting mechanism due to the required space needed to incorporate the parallel shifting linkages, and thus is limited to applications where the shift control lever can be rigidly mounted to a frame or other non-movable part of a vehicle body. The space required for the shift linkages is considerable and as it must be kept clear of obstacles for movement of the shift linkages, results in an inefficient use of space and is typically limited to automotive applications.
Another disadvantage of the shift mechanism is the considerable lateral and longitudinal movement required of the shift control lever to control the shift linkages to engage the transmission in the desired gear. The degree of movement increases as the number of gear ratios available from the transmission increases.
Gear shifting mechanisms are also used in recreational vehicles, such as motorcycles and three- or four-wheel vehicles. Typically these recreational vehicles utilize small gas motorcycle engines having conventional motorcycle transmissions. One example is the engine and transmission manufactured by Harley-Davidson. In the three- or four-wheeled application, the motorcycle and transmissions are adapted from a two-wheel application. A disadvantage is that the motorcycle transmission does not typically have a reverse gear capability as does the manual shift multi-speed transmission used for automotive and other larger vehicle applications. Another disadvantage is these typically utilize high-maintenance chain or belt drives to drive a rear axle associated with the rear drive wheels, and have no means to associate the motorcycle engine with higher reliability automotive transmissions or transaxels having fully enclosed drive trains such as those manufactured by Volkswagen. The automotive transmissions or transaxels are limited in this application due to the required space needed to incorporate the parallel shifting linkages with conventional shifting mechanism. These are also limited as the shift control lever must be rigidly mounted to a frame or other non-movable part of the vehicle body. Current gear shifting mechanisms however still lack the requisite low weight and compact design required for the recreational vehicle applications.